epd4in2¶

Driver for the Waveshare 4.2” e-Paper module V2 / Rev2.2 (SSD1683, 400x300 b/w).

Command sequence follows Waveshare’s epd4in2_V2 reference driver. The image is a MONO_HLSB buffer (bit set = white), e.g. a framebuf.FrameBuffer’s bytearray, sent as is.

Pins are injected machine.Pin-like objects, so the driver runs on the host against fakes. pwr is optional: Rev2.2 modules switch the panel supply with it, and EPD.power_off cuts it (see defaults.DISPLAY_OFF_IN_SLEEP).

Black/white RAM and “red RAM”. The SSD1683 controller has two image memories of one bit per pixel. The controller family also drives black/white/red panels, where the second memory holds the red layer; hence its name in the datasheet, “red RAM”. On this black/white panel it has another use: a full refresh (EPD.display) only shows the black/white RAM, while a partial refresh (EPD.display_partial, EPD.display_band) treats the red RAM as the image the panel shows now and drives only the pixels in which the black/white RAM differs from it. That is why it flashes less and is faster, and why it goes wrong if the red RAM does not hold what the panel really shows: pixels the controller believes unchanged are left as they are.

The red RAM cannot be relied on after EPD.init: on a Rev2.2 module it no longer held the previous image on the next wake (partial updates left old and new digits overlaid), whether through the reset or the deep sleep in between. A partial refresh therefore needs the image the panel shows passed in as the old one, which the driver writes into the red RAM first; the firmware keeps a copy on flash for that (screen). After each update the driver stores the new image in the red RAM as the old one for a following update without EPD.init.

Attributes¶

`WIDTH`
`HEIGHT`
`BUFFER_SIZE`

Classes¶

EPD

Driver for the 4.2" SSD1683 panel on injected SPI and pins.

Module Contents¶

epd4in2.WIDTH = 400¶

epd4in2.HEIGHT = 300¶

epd4in2.BUFFER_SIZE = 15000¶

class epd4in2.EPD(spi, cs, dc, rst, busy, pwr=None, sleep=time.sleep)¶

Driver for the 4.2” SSD1683 panel on injected SPI and pins.

spi¶

cs¶

dc¶

rst¶

busy¶

pwr = None¶

sleep¶

wait_until_idle(timeout_s=30)¶

Wait while BUSY is high, that is while the controller works.

Raises:: OSError – If the controller stays busy for more than timeout_s.

reset()¶: Reset the controller by its pin (this also ends its deep sleep).

init()¶: Power up, reset and configure for full-screen updates.

display(buffer)¶: Full refresh with buffer (BUFFER_SIZE bytes, MONO_HLSB).

display_band(old, new, y0, y1)¶

Partial refresh of the full-width rows y0..y1 without flashing.

old must be what the panel shows there now and new the target image, both (y1 - y0 + 1) * WIDTH // 8 bytes (MONO_HLSB). Rows outside the band are not touched.

display_partial(buffer, old=None)¶

Refresh the whole screen without flashing.

The update compares against the red RAM, which must hold what the panel shows. Pass that image as old: after init the red RAM is blank, and pixels would then only turn black, never back to white. Without old this works only for updates without an init since the previous one. Use a full display now and then against ghosting.

Parameters:

buffer – The new image (BUFFER_SIZE bytes, MONO_HLSB).
old – The image on the panel, if the controller lost it.

Raises:

ValueError – If a buffer has the wrong size.

sleep_mode()¶

Put the controller into deep sleep mode 1.

The panel keeps its image. Call init before the next update; its red RAM may not hold the image any more afterwards.

power_off()¶: Cut the panel supply (Rev2.2); the next update must be a full one.